RDF for Web server config

Context: this is a quick note that I put
together sometime during 1999 for the Jakarta/tomcat discussions.
Copied to a more long-term location here for reference. I'm pleased
to say that my original claim ('weakly integrated with the rest of
the XML infrastructure') is beginning to sound dated. See RDF Interest Group
archives for discussion of XSLT, XLink etc. for details of more
recent work in that direction.

Jakarta XML/RDF examples

This is just a very quick example to illustrate some of the
design tradeoffs involved with the use of RDF and its XML syntax.
Basically, you get a simple conceptual model (directed labelled
graphs) at the cost of some syntactic verbosity. RDF is good at
drawing upon multiple namespaces/vocabularies simultaneously, and
is hence strong on re-use and modularity. It is currently rather
weakly integration with the rest of the XML infrastructure (XSL,
DTDs etc), although there is work in progress to improve this.

The example below shows a snippet of configuration that tells us
about an object of rdf:type Server, one of its modules, and the
properties of that module, a sample directory and associated
persons. Note that the directed labelled graph model, although
simple, requires the XML/RDF syntax to make explicit certain
relationships between objects that would likely be left implicit in
vanilla XML. For example, the 'dir' relationship between the Server
and the Directory objects seems redundant, but it allows us to draw
out a graph representation of the specified data more easily.

The details of the syntax will not make sense without knowledge
of the RDF syntax; the 'triples' file below shows the output of the
W3C RDF parser SiRPAC when fed this data. We might imagine query
APIs for the resulting information that could also query data from
LDAP etc, ie. not care about the XML representation but deal
straight with the underlying graph model.

I've annotated the XML inline to explain more or less what's
happening with the syntax. Any questions just ask...